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Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, and unrealized gains and losses on certain investments in debt and equity securities as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge. 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Note: elements for number of nonredeemable preferred shares, par value and other disclosure concepts are in another section within stockholders' equity. 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No authoritative reference available. true 30 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 32 Washington Gas Light Company preferred stock 2 us-gaap_MinorityInterestAmountRepresentedByPreferredStock us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 28173000 28173 false false false 2 false true false false 28173000 28173 false false false xbrli:monetaryItemType monetary The amount of noncontrolling interest in subsidiary represented by preferred securities issued by the subsidiary. 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No authoritative reference available. true 43 Washington Gas Light Company | Due fiscal year 2010, 1.19% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 9 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 10 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 55 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 56 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0 0 false false false 2 false true false false 50000000 50000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 64 Washington Gas Light Company | Due fiscal year 2010, 7.50% to 7.70% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 11 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 12 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 76 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 77 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0 0 false false false 2 false true false false 24000000 24000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 85 Washington Gas Light Company | Due fiscal year 2011, 6.64% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 13 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 14 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 97 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 98 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 30000000 30000 false false false 2 false true false false 30000000 30000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 106 Washington Gas Light Company | Due fiscal year 2012, 5.90% to 6.05% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 15 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 16 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 118 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 119 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 77000000 77000 false false false 2 false true false false 77000000 77000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 127 Washington Gas Light Company | Due fiscal year 2014, 4.88% to 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 17 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 18 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 139 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 140 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 67000000 67000 false false false 2 false true false false 67000000 67000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 148 Washington Gas Light Company | Due fiscal year 2015, 4.83% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 19 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearSixMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSixMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 20 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearSixMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSixMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 160 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 161 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 20000000 20000 false false false 2 false true false false 20000000 20000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 169 Washington Gas Light Company | Due fiscal year 2016, 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 21 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearSevenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSevenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 22 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearSevenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSevenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 181 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 182 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 25000000 25000 false false false 2 false true false false 25000000 25000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 190 Washington Gas Light Company | Due fiscal year 2019, 7.46% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 23 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearEightMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearEightMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 24 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearEightMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearEightMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 202 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 203 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 50000000 50000 false false false 2 false true false false 50000000 50000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 211 Washington Gas Light Company | Due fiscal year 2020, 4.76% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 25 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearNineMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearNineMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 26 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearNineMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearNineMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 223 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 224 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 50000000 50000 false false false 2 false true false false 0 0 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 232 Washington Gas Light Company | Due fiscal year 2023, 6.65% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 27 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearTenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 28 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearTenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 244 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 245 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 20000000 20000 false false false 2 false true false false 20000000 20000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 253 Washington Gas Light Company | Due fiscal year 2025, 5.44% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 29 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearElevenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearElevenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 30 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearElevenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearElevenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 265 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 266 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 40500000 40500 false false false 2 false true false false 40500000 40500 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 274 Washington Gas Light Company | Due fiscal year 2027, 6.40% to 6.82% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 31 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearTwelveMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwelveMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 32 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearTwelveMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwelveMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 295 Washington Gas Light Company | Due fiscal year 2028, 6.57% to 6.85% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 33 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearThirteenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThirteenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 34 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearThirteenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThirteenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 307 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 308 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 52000000 52000 false false false 2 false true false false 52000000 52000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 316 Washington Gas Light Company | Due fiscal year 2030, 7.50% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 35 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFourteenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 36 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFourteenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourteenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 328 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 329 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 8500000 8500 false false false 2 false true false false 8500000 8500 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 337 Washington Gas Light Company | Due fiscal year 2036, 5.70% to 5.78% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 37 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFifteenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFifteenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 38 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_UnsecuredMediumTermNotesDueInYearFifteenMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFifteenMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 358 Washington Gas Light Company | $4.80 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 39 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 40 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 366 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 368 Washington Gas Light Company preferred stock 2 us-gaap_MinorityInterestAmountRepresentedByPreferredStock us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 15000000 15000 false false false 2 false true false false 15000000 15000 false false false xbrli:monetaryItemType monetary The amount of noncontrolling interest in subsidiary represented by preferred securities issued by the subsidiary. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 27 -Article 5 false 379 Washington Gas Light Company | $4.25 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 41 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 42 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 387 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 389 Washington Gas Light Company preferred stock 2 us-gaap_MinorityInterestAmountRepresentedByPreferredStock us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 7173000 7173 false false false 2 false true false false 7173000 7173 false false false xbrli:monetaryItemType monetary The amount of noncontrolling interest in subsidiary represented by preferred securities issued by the subsidiary. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 27 -Article 5 false 400 Washington Gas Light Company | $5.00 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 43 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 44 USD true false false false us-gaap_SubsidiariesMember dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 408 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 410 Washington Gas Light Company preferred stock 2 us-gaap_MinorityInterestAmountRepresentedByPreferredStock us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 6000000 6000 false false false 2 false true false false 6000000 6000 false false false xbrli:monetaryItemType monetary The amount of noncontrolling interest in subsidiary represented by preferred securities issued by the subsidiary. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 27 -Article 5 false 421 Due fiscal year 2010, 1.19% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 45 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 46 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 433 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 434 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0 0 false false false 2 false true false false 50000000 50000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 442 Due fiscal year 2010, 7.50% to 7.70% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 47 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 48 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 454 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 455 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0 0 false false false 2 false true false false 24000000 24000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 463 Due fiscal year 2011, 6.64% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 49 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 50 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 475 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 476 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 30000000 30000 false false false 2 false true false false 30000000 30000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 484 Due fiscal year 2012, 5.90% to 6.05% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 51 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 52 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 496 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 497 Total Unsecured Medium Term-Notes 2 us-gaap_MediumTermNotes us-gaap true credit instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 77000000 77000 false false false 2 false true false false 77000000 77000 false false false xbrli:monetaryItemType monetary Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5 false 505 Due fiscal year 2014, 4.88% to 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalization false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 53 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 54 USD true false false false wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. 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